LAS develops systems for computer-based mathematical analysis, pattern recognition and image processing in support of diagnostic activities in the Nuclear Medicine Department of the Clinical Center and collaborating Institutes. Many applications are directed toward the correlation of function with structure, such as: estimation of ventricular function from radionuclide ventriculography or PET scan (functional data) compared to MRI or CT scans (anatomical data). The primary application has been in the analysis, registration, and segmentation of cardiac image data. An automated system has been developed for three-dimensional registration of cardiac PET emission data for a subject over repeated studies without use of fiducial points or contours. Systems are being developed for the creation of sequences of projections of volumetric data, alignment of projection to tomographic data and for application of two-dimensional regions-of-interest to translated and rotated volumetric data. Other problems involve projection of volumetric data to a two-dimensional CRT screen in ways that are meaningful and useful to researchers and the problem of how best to visualize volumetric PET superimposed on an MRI or CT volume with variable levels of transparency. Computer platforms used in this project include the Vax, Macintosh, IBM-compatible PC, and UNIX workstations. LAS, in collaboration with the Nuclear Medicine Department of the Clinical Center has, over the past six years, designed and specified a general-purpose image processing system, MIRAGe. Programming was performed by contractors supervised by LAS and the Nuclear Medicine Department. The completed basic system has been ported to several other NIH computer systems including Vax workstations and Macintosh systems. Many academic and commercial institutions across North America and Europe have requested and received copies of the system. Work has begun on the next generation system based on a UNIX workstation. This system will incorporate the functionality of MIRAGe with advanced 3D visualization, analysis and registration capabilities.